Application Note

Practical Tips On Measuring Interference

By utilizing the ISM (Industrial-Scientific-Medical) frequency bands, the wireless industry has been able to exploit
the increasing popularity of unlicensed communication systems. However, their unlicensed nature carries with it
the seeds of serious signal interference problems. As described in the "Fundamentals of Interference in Wireless
Networks" application note, such ISM system designs are type-approved but are then installed by unlicensed owners or
contractors. These conditions sometimes
lead to signal configurations that unintentionally interfere.

When ISM technologies are applied to Wireless LAN applications, the radiated signals are essentially contained
within one building. Even though other systems may be installed on adjacent floors or even on the same floor,
those systems are designed to perform well in proximity to each other. Transmitter power is low, antenna gain is
minimal, and modulation schemes are designed to overlap without interfering with each other.

The objective of this article is to present measurement tips and procedures which will help a field technician measure signal interference in operating communications systems.